The present invention relates to reciprocating pumps in general, and more particularly to improvements in reciprocating pumps of the type wherein a plunger is surrounded by a sleeve-like tubular member which receives fluid from the inlet of the pump housing during each return stroke of the plunger and from which pressurized fluid is expelled when the plunger performs a forward stroke. As a rule, such pumps are used for effecting pronounced pressurization of a liquid on its way from the inlet or inlets to the outlet or outlets of the pump housing.
In presently known pumps of the just outlined character, the tubular member performs the function of a suction valve. To this end, the tubular member is reciprocable in the pump housing so as to permit fluid to flow from the inlet (and more particularly from a chamber which is defined by the tubular member and the pump housing) into its interior while the plunger moves away from the delivery valve and to seal its interior from the inlet while the plunger performs a forward stroke. A drawback of such pumps is that the mass of the tubular member is large so that the tubular member cannot reciprocate with a sufficient degree of reproducibility when the plunger is driven at a high speed.